In optical systems which involve the transmission of guided light between two locations, there is often a need for dividing light that has been transmitted along one or more channel waveguides among several channel waveguides for further transmission.
Typically, M.times.N prior art couplers have been complex and not easily manufactured or else have been inefficient and have provided undesirably wide variations in the degree of coupling between different ports. The present invention seeks to provide a coupler with M.times.N ports that is easy and relatively inexpensive to fabricate.